Bartonite

Formula:  K₃Fe₁₀S₁₄

Origin of name:  For Paul B. Barton Jr., American petrologist with the U.S. Geological Survey

Crystal system: Tetragonal

Crystal class:  4/m 2/m 2/m

Twinning:

Unit cell: a = 10.424 Å, c = 20.626 Å

Colour:  Blackish-brown

Diaphaneity: submetallic

Luster:  Submetallic

Habit:  As anhedral grains, intergrown with pyrrhotite; single crystals rare, less than 5 μm wide and 5 to 10 times as long

Hardness:  3

Specific gravity:  3.305

Cleavage:  1; {112} distinct

Tenacity: conchoidal fracture

Streak:  Black

Synonyms/varieties:

Comments: Found in clots with other sulfides and silicates in an alkalic diatreme intruding Franciscan rocks